EU261/2004 does apply to transit passengers even if weather is a factor. There’s been a clarification on this. Even if a previous flight operated by the aircraft affected by weather is included. All of this, however, depends on the arrival time at destination compared to scheduled arrival time. The arrival has to be 3h+ late. Also depends on the airline you’re dealing with if they are on your side or not and sadly LH group airlines (of which Austrian belongs to) are not renowned for paying up, even when required to.

this should help a little bit: Passenger rights Fact Sheets on the European Union European Parliament